Transverse-load-induced electromechanical degradation and damage evolution in TSSC REBCO cables

Abstract

Large transverse Lorentz forces in high-field superconducting magnets pose severe challenges to the mechanical integrity and operational reliability of REBa2Cu3O7− δ (REBCO) conductors. However, cable-scale electromechanical studies above 103 kN m−1 remain rare, and the mechanics-to-performance degradation pathway of mechanically heterogeneous, solder-encapsulated REBCO cables remains poorly understood, impeding technological advancement. In this study, cryogenic electromechanical experiments at 77 K were integrated with three-dimensional finite-element simulations to quantify the monotonic and cyclic transverse-load responses of twisted stacked slotted-core (TSSC) REBCO cables and provide mechanics-based interpretations of damage susceptibility. Monotonic tests reveal a pronounced loading-orientation effect: at 95% critical-current retention, the cable sustains 2080 kN m−1 under 0° loading, approximately 33% higher than the 1560 kN m−1 sustained under 45° loading. Simulations further link this difference to orientation-dependent load redistribution, resulting in distinct spatial patterns of local plasticity and solder damage initiation, together with corresponding variations in the mixed-mode interlaminar damage-driving index near the REBCO tape edges. Additionally, cyclic tests reveal load-level-dependent degradation behavior: at 1500 kN m−1, the cable exhibits a three-stage degradation process with accelerated degradation after approximately 900 cycles, whereas at 1375 kN m−1, the critical current remains nearly unchanged after 1000 cycles. Moreover, cross-sectional observations identify solder voids and insufficiently filled regions as processing-induced defects, while defect-containing finite-element models show that these defects amplify local stresses and disrupt load-transfer continuity. These findings establish a contact–plasticity–damage failure pathway and provide mechanics-based guidance for defect control and structural optimization of reliable TSSC conductors.